JP3086711B2 - Casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold casting method, and more particularly to a novel casting method suitable for manufacturing articles having a rotating body shape such as a substantially cylindrical shape or a substantially bowl shape. It is.

[0002]

2. Description of the Related Art Light alloy wheels of automobiles, which are representative of such articles, are described. Aluminum wheels are used for the purpose of reducing rotational load, reducing vehicle weight, improving aesthetic appearance, and the like. Since the parts are directly related to safety, those having high quality and excellent strength are desired. As a method of manufacturing light alloy wheels represented by aluminum alloys and magnesium alloys,
A gravity die casting method, a low pressure casting method, a molten metal forging method (squeeze casting method) and the like are generally performed.

[0003] Among the above-mentioned production methods, the gravity mold casting method is the most widely used because the equipment and the mold are inexpensive.
As shown in FIG. 3, although the target molded product P is substantially cylindrical, the pouring gate 50 must be provided on the side of the cylindrical molded product. In the mold, the part close to the sprue draws heat from the molten metal and becomes considerably high temperature, while the part far from the sprue decreases on the contrary, so that solidification becomes unstable and products are likely to have defects. There are drawbacks. Also, in gravity die casting, it is difficult to manufacture thin-walled products or products with complicated shapes unless the die temperature is maintained at a high temperature in order to improve the flow of the molten metal. It takes a long time to work, and productivity becomes worse.
Since the time during which the temperature is maintained at a high temperature becomes longer, the structure of the casting becomes coarse, and in the case of a tubeless tire, there is a disadvantage that air leakage occurs. Reference numeral 51 denotes a feeder section.

[0004] The low-pressure casting method uses a lower mold 6 as shown in FIG.
4. A closed cavity 60 having a desired light alloy wheel shape by the horizontal split molds 61, 62 and the upper mold 63.
Is provided below the mold, a closed holding furnace 66 is provided, and a pressure of 0.1 to 0.3 atm is applied to a molten metal surface of the holding furnace to raise the molten metal in the stalk. Hot water is supplied to the cavity 60 through a gate 65 provided at the center of the lower mold. This method is easy to automate, does not require a riser because the molten metal is pressurized during solidification, and can also respond to products with complicated shapes, as compared with the gravity mold casting method. There are many advantages, but on the other hand, the cost of the molds and machinery is high for the obtained productivity. The melt moves up and down in the stalk each time it is performed, and along with this, the dirt in the stalk and the oxide film formed by oxidizing the melt adhering to the inner surface of the stalk are easily peeled and mixed into the product, and during solidification, Since pressure is applied to the molten metal, there is a drawback that harmful abnormal segregation may occur depending on the type of the molten metal, which may result in a product defect.

[0005] The molten metal forging method completes solidification while pressurizing the molten metal at a high pressure of 500 to 1000 kg / cm ² in a closed mold.
In addition to the enormous cost, the solidification under high pressure causes harmful segregation depending on the composition of the molten metal.

Further, in each of the above-mentioned methods and the special die casting method, it is essential that a predetermined amount of hot water is supplied quickly through a gate so as not to lower the temperature. Therefore, when the molten metal passes through a sprue with a small cross-sectional area at high speed, turbulence occurs in the molten metal, and there is a high possibility that air inside the mold is caught in the product at the time of molding. Defects such as were easy to occur.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the conventional casting method and to provide a product having a rotating body shape typified by a light alloy wheel without requiring excessive equipment costs. It is an object of the present invention to disclose a new casting method that can be efficiently produced with high quality.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is that a lower mold and a splittable horizontal mold are combined to form a container-like mold having a desired molding inner surface, and a predetermined amount of molten metal is poured into the container-like mold. By lowering the insertion mold having a desired molding outer surface in the container-shaped mold while excluding the molten metal, the molten metal is gently raised in a gap formed between the inner surface of the container-shaped mold and the outer surface of the insertion mold. So that the gap expands near its upper end.
By the rising molten metal,
Forming a hot water part that circulates around the upper end of the gap, at the position forming the target object, stopping the insertion mold, solidifying the molten metal in a state where the upper end surface of the molten metal is open to the atmosphere, and using a conventional method. On the basis of this, the target molded product is removed from the mold and subjected to finish processing. There is provided a method of casting a product having a shape such as a substantially bowl shape or a substantially cylindrical shape having an opening that allows insertion of an insertion mold in at least one of the axial directions. Hereinafter, a detailed description will be given based on an embodiment.

FIG. 1 and FIG. 2 schematically show a method according to an embodiment of the present invention, taking the case of casting of a light alloy wheel for a vehicle as an example. In the method of the present invention, first, a lower mold 1 provided with a coating material and horizontal dies 2a and 2b which can be divided into two in the left-right direction are assembled into a container-shaped mold A having an opening at an upper part, and appropriate known means is used. By
Fix it. At this stage, the inner surface of the container-shaped mold A forms the target aluminum wheel outer shape in a positional relationship in which the virtual center axis of the substantially bottomed cylindrical aluminum wheel stands upright at the center of the bottom. The coating material is desirably made of a heat retaining material. By gently injecting a predetermined amount of aluminum alloy into such a container-shaped mold A, the molten metal M is firstly filled with a cavity (cavity) 3 previously formed by the lower mold 1 and the horizontal molds 2a, 2b. And then cover the bottom surface to a predetermined height.

[0010] Here, without delaying the time, the insertion mold B, which has been set up, is immediately brought to the upper side of the opening of the container-shaped mold, is lowered, and is inserted into the container-shaped mold A. From 6,
The molten metal M is caused to enter. Accordingly, the molten metal M removed by the insertion mold rises in the gap 5 formed by the side surface 7 of the insertion mold B and the inner wall surface 4 of the container-like mold A.
The ascending speed adjusts the descending speed of the insertion mold so as to be a sufficient safe speed that does not generate turbulence in the molten metal. It goes without saying that the outer surface of the insert mold is a forming outer surface on which the inner surface of the light alloy wheel is to be formed. Thus, molten metal M
Rises in a state in which only the upper end surface is in contact with the atmosphere, and reaches the hot water forming portion 5a formed by rapidly and uniformly increasing the thickness near the upper end of the gap 5. Then, when the lower peripheral edge portion 8a of the heat retaining lid 8 provided integrally with the upper portion of the insertion mold comes into contact with the upper peripheral edge 2c of the container-shaped mold A,
As shown in FIG. 2, a gap formed between the lower end surface 6 and the side surface 7 of the insertion mold and the inner surface of the container-shaped mold forms the shape of the target molded product 20, and the ring extends along the feeder forming portion 5 a. A feeder portion 21 in a shape of is formed. By leaving it in this state for a predetermined time, the solidification of the molten metal is completed. Then, the insertion mold moves upward and separates, and the horizontal molds 2a and 2b are divided to take out the target casting 20.

FIG. 5 shows another embodiment according to the present invention.
Conventionally, as shown in FIG.
By manufacturing the vehicle rim 30 having the mounting portion 34 of the disk 39 near the center of the inner surface of the substantially cylindrical body by welding the first and second 32 at the joint 33, the method of the present invention is applied. This shows a case where this is cast as one member. In FIG. 5, 11 is a lower mold, 12
a and 12b are left and right horizontal types, and 10 is an insertion type. The difference from the above embodiment is that the lower mold 11 is provided with a basin section 11a capable of storing a required total amount of molten metal below the molding section 23 where the product disk mounting section is to be molded. The insertion mold 10 is provided with an exclusion part 10a for entering the basin part 11a to eliminate and raise the molten metal M. The exclusion portion gently raises the molten metal, and then gently overflows the molten metal into a thin-walled space 25 having a large drop formed by the lower mold 11 and the horizontal molds 12a and 12b. The purpose is to allow the air to flow down quickly and quietly without involving air. Therefore, the exclusion part 11a does not have a molded surface of the product. Other operations such as the operation of the insertion mold 10 are completely the same as those of the above embodiment. In the case where the space previously formed in the container-shaped mold is thin and the flow path for hot water supply is long as described above, there is no danger of air being caught in the product by providing the water reservoir in advance. .

Each of these steps can be easily automated by employing a water heater used in general gravity mold casting or a mold moving mechanism using a hydraulic cylinder or the like. The casting obtained in this manner is processed into a predetermined shape by a cutting tool or the like by appropriately removing a feeder portion and the like. Further, if necessary, this is subjected to anodizing treatment such as alumite treatment and other surface treatment.

[0013]

[Effect Based on the above method, using Al-Cu-Mg alloy (JIS AC-1B), light alloy wheels produced has a tensile strength: 38~40Kg / mm ^2, 0.2% proof stress: 25 ２６26 Kg / mm ² , elongation: 18-22%. This value greatly exceeds the value of the JIS 6000 forged product, and is the highest value of a light alloy wheel manufactured by gravity die casting using an Al-Si-Mg based alloy (JIS AC-4C). Close data, tensile strength: 28 kg / mm ² , 0.2% proof stress: 24 K
g / mm ² , elongation: 10%, which is much better.

In the casting method of the present invention, hot water is supplied directly into the mold without going through the gate system, so that the hot water supply time is extremely short, there is no local heating of the mold, and the insertion mold is As it enters, the gap rises by the amount of the molten metal removed by the insertion mold, so when the molten metal fills the gap, it rises slowly without any turbulence, aligning its height in the circumferential direction. There is no turbulence in the gate system as seen in conventional die casting, and there is no air entrapment, no defects such as pinholes and blowholes are generated, and hot water supply is performed quickly and in the circumferential direction. Since it is performed uniformly, it can be applied to extremely thin products, and the feeder is uniformly formed in the circumferential direction, so that the heat distribution in the circumferential direction becomes uniform and almost uniform along the axial direction. Temperature gradient occurs, directivity The solid is realized, further, upon solidification of the molten metal, since a pressure above gravity is not applied, C
For example, by using the AC-1B alloy, there is an advantage that the alumite treatment is facilitated and the product value can be enhanced because no harmful segregation occurs even when a u-based aluminum alloy or the like is used. .

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing one embodiment of a casting method according to the present invention.

FIG. 2 is a perspective view of the container-shaped mold and the insertion mold shown in FIG.
It is explanatory drawing which shows the state which shape | molded the target molded object.

FIG. 3 is an explanatory view showing a molded product by a gravity mold casting method.

FIG. 4 is an explanatory diagram showing an example of a low-pressure casting method.

FIG. 5 is an explanatory diagram showing another embodiment of the present invention.

FIG. 6 is a sectional view showing a vehicle rim manufactured by a conventional method.

[Explanation of symbols]

 1 Lower mold 2a, 2b Horizontal type A Container type B Insert type M Molten metal

Claims (4)

(57) [Claims] 1. A container-shaped mold having a desired molding inner surface is formed by combining a lower mold and a splittable horizontal mold, and a predetermined amount of molten metal is poured into the container-shaped mold. By lowering the insertion mold having the desired molding outer surface while excluding the molten metal, the molten metal is gently raised in a gap between the inner surface of the container-shaped mold and the outer surface of the insertion mold, and the gap is Expand near its upper end
By being configured as described above,
After forming a feeder part which circulates around the upper end of the gap , the insertion die is stopped at a position where the shape of the object is formed, and the molten metal is solidified in a state where the upper end surface is open to the atmosphere. A casting method characterized by taking out a target molded product from a mold based on the above and subjecting it to finish processing. 2. A basin is formed on an inner bottom surface of the container.
After the required amount of molten metal has been injected into the well,
The molten metal that is removed by the insertion mold that enters
Voids overflowing and pre-formed by horizontal and lower molds
2. The casting method according to claim 1, further comprising the step of filling a part. 3. The casting method according to claim 1, wherein the molten metal is a light metal alloy, and the target molded product is a vehicle molten light alloy wheel. 4. A combination of a lower mold and a splittable horizontal mold.
Forming a container-shaped mold with a molded inner surface for light alloy wheels for vehicles
Yes forms, after injecting a predetermined amount of light alloy molten metal in the vessel-shaped mold, into the container-shaped mold, molding the outer surface of the light alloy vehicle wheel
By lowering the insertion mold while removing the molten metal.
And the inner surface of the container mold and the outer surface of the insertion mold
Gently raise the gap to make the gap
The insertion mold is stopped at the position where
After solidifying with the top surface of the hot water open to the atmosphere,
From the mold based on the
Casting method, wherein the casting is performed.